The present invention relates to instrumentation for long term monitoring of fine particles in gas streams, such as stack emissions of combustion systems and industrial equipment generating soot, ash, dusts, granules and other fine particles.
The means for such monitoring include optical, radioactive, acoustic and electric transducers. Each has its unique merits and drawbacks. There are also a number of common drawbacks. Some of the common drawbacks include drift of transducers and circuits. Off-line calibration is impractical in many usages.
It is an object of the invention to provide an electric transducer and circuit which reliably monitors stream conditions over a long term.